Communication cable



Sept. 6, 1966 H. BURR COMMUNICATION CABLE Filed April 30, 1965 INVENTOR.

HARVEY BURR United States Patent 3,271,508 COMMUNICATION CABLE HarveyBurr, De Kalb, Ill., assignor to Anaconda Wire and Cable Company, acorporation of Delaware Filed Apr. 30, 1965, Ser. No. 452,225 4 Claims.(Cl. 174-113) My invention relates to communication cables andparticularly to cables having a large plurality of twisted parsinsulated with longitudinal tapes.

In my US. Patent 3,053,037 there is described an apparatus for applyingpaper tapes to telephone conductors straight-away while, at the sametime, twinning the conductors to form twisted pairs. The productproduced by this apparatus will have the paper insulation wrapped, ineffect, with the same length of lay as the law of twist of the pair. Inmy applications, Serial Nos. 383,335 and 409,898, I have disclosed diessuitable for applying paper or other tapes around metal wires,straight-away with a longitudinal scam.

I have now discovered that when the pairs made with 'my longitudinaltape insulation are formed into cables of large size in the manner, andso as to form a cable structure, hereinafter to be described, the cablehas unexpected properties and advantages.

It is an object of my invention to make a telephone cable with a largeplurality of conductor pairs, at low cost.

It is a further object of my invention to make a telephone cable havinga large plurality of conductor pairs of more than usual reliability.

It is a further object of my invention to make a large diametertelephone cable resistant to mechanical abuse.

I have invented a communication cable which comprises a largepluralityof twisted pairs of insulated conductors with all of the pairstwisted with the same direction of lay. Each conductor of my cable isindividually wrapped with approximately a double layer of spiralledinsulating tape, such as paper, having a wrapping lay the same as thelength of lay of twist of the pair that includes the conductor. Thedirection of spiral of the paper on all the conductors of the cable isthe same. The pairs themselves are cabled together with a length of layexceeding the length of lay of any of the component pairs twists, andthere is a sheath surrounding the cabled conductors.

My cable may have a first plurality of conductor pairs cabled into afirst core unit and at least a second plurality of pairs cabled into asecond unit with the core units themselves helically twisted to form thecable core.

A more thorough understanding of my invention may .be gleaned from astudy of the appended drawing.

In the drawing:

FIGURE 1 shows a lengthwise section of a cable made to my invention.

FIGURE 2 shows an enlarged section of an insulated conductor used in myinvention.

FIGURE 3 shows an enlarged section taken through the conductor at 33having insulation spiralled in a direction opposite to that of theconductor of FIGURE 2.

FIGURE 4 shows a cable core made in accordance with my invention.

My cable indicated generally by the numeral comprises a large plurality,by which I means at least 25, of pairs 11, each pair being made bytwisting together 2 insulated conductors 12, 13. The insulation on eachof the conductors consists of a spiralled paper that is applied with aseam 16 running lengthwise. In other words the paper is not helicallywrapped around the conductors in the manner customary in thecommunication cable art but has a uniform spiral with a longitudinaledge, most clearly shown in FIGURE 3. In the twisted pairs 11 the edges16 do have a helical twist around the conductors "ice but this wasimparted during the twisting of the pairs and the length of lay of thisspiral is the same as the length of lay l of the pair twist. Bycontrast, in the conventional wrapping of telephone paper insulationthere are ten or more wraps of paper for each lay length of the pair. Asshown in FIGURE 3 the spiral of the paper wrap is seen to be lockwisewhile the spiral of FIGURE 2 is counterclockwise. It is a feature of mycable 10 that all the conductors are insulated with a clockwise Wrap.They might equally effectively all be insulated with a counterclockwise(FIGURE 2) wrap, but it should be noted that the cables that were testedand found to have unexpected advantages, as hereinafter to be described,had all the conductors wrapped in the same direction.

As illustrated in FIGURE 1 the pairs 11 are all twisted with a left handlay. My cable is equally satisfactory if all the pairs are twisted witha right hand lay, but it is a feature of my cable, showing unexpectedadvantages, that the direction of lay of all the pairs are the same,either left-hand or right-hand.

To form a cable core the pairs 11 have been cabled together with a righthand spiral in a long lay. I have designated the length l as marking thelength of lay of one of my pairs 11 but it will be understood that thelength of lay of adjacent pairs will always be varied in the usual knownmanner for the purpose of avoiding cross talk. The length of lay may beuniform for any pair or it may also vary along the length of the pair,but the length of lay of the cable core formed by the twisted pairsthemselves, exceeds the maximum lay of pairing of any of the pairs atany point.

In FIGURE 4 a plurality of the pairs 11 have been stranded to form acore unit 21, a second plurality of pairs have been stranded into theunit 22, and a third plurality has been stranded into a unit 23. Thethree units have then been cabled into a cable core 24 and covered by ametal sheath 26. The core 24 is characterized by having the samedirection of lay on all the pair twists and the same direction of spiralof all the insulation wraps.

Cables made in accordance with my invention having a large plurality ofpairs, by which I mean at least 25 pairs, have been found to have anentirely unexpected advantage in ruggedness over convention-a1 helicallywrapped or even pulp-insulated cables. The advantage appears to beassociated with the manner in which the pairs oan slide relative to eachother when the cable is flexed sharply or stretched. The advantage showsup particularly when .the cable sheath has been dented or necked down.In a conventional helically insulated cable the insul-ations tend tobunch up at the constricted area and to create bare spots all at onepoint where they oan short against each other. Furthermore, the bunchedup paper in the constricted zone tends to jam the conductors so that,instead of stretching harmlessly over a long length where it may notexceed the elastic limit, whatever elongation of the conductors may takeplace due to flexing or stretching of the cable sheath is confined to ashort distance where it may be enough to break the conductors or toincrease their electrical resistance beyond acceptable limits.

When the new cable is destructively tested in a tensile machine it isfound that the insulation breaks are distributed throughout the lengthof the test sample, Whereas the breaks in a helical-wrap-insulated cableor, for that matter, a pulp-insulated cable, are concentrated Within ashort length of the sample. During tensile testing my new cable, havinga large plurality of pairs, absorbed more than ten times .the energyabsorbed by a helicalwrap-insulated cab-1e before the conductors startedto break. This enables my new cab-1e -to better withstand a jerk duringinstallation and, if the jerk is sufficient'ly violent to cause paperbreaks, to have less chance of developing a cross or short.

I have invented a new and useful cable for which I desire an award ofLetters Patent.

1 claim:

1. A communication cable comprising a large plurality of twisted pairsof insulated conductors,

I (A) all of said pairs or" conductors being twisted with the samedirection of lay,

(B) each conductor being individually wrapped with an approximatelydouble layer of spiralled insulating tape having a length of wrappinglay equal to the length of lay of twist of the pair comprising saidconductor,

(C) the direction of spiral of the tape on all conductors in said cablebeing the same,

(D) said pairs being cabled together in a helix having a length of layexceeding the length of lay of any of the component pair twists, and

(E) a sheath surrounding said cabled conductors.

2. A communication cable comprising a large plurality of twisted pairsof insulated conductors,

(A) all of said pairs of conductors being twisted with the samedirection of lay,

(B) each conductor being individually wrapped with an approximatelydouble layer of spiralled insulating paper having a length of wrappinglay equal to the length of lay of twist of the pair comprising saidconductor,

(C) the direction of spiral of the paper on all conductors in said cablebeing the same,

(D) said pairs being cabled together in a helix having a length of layexceeding the length of lay of any of the component pair twists, and

(:E) a sheath surrounding said cabled conductors.

*3. A communication cable comprising a large number of twisted pairs ofinsulated conductors,

(A) all of said pairs of conductors being twisted with the samedirection of lay,

(B) each conduct-or being individually wrapped with an approximatelydouble layer of spiralled insulating tape having a length of wrappinglay equal to the length of lay of twist of the pair comprising saidconductor,

(C) the direction of spiral of the tape on all conductors in said cablebeing the same,

(D) a first plurality of said pairs being cabled together in a helixhaving a length of lay exceeding the length of lay of any of thecomponent pair twists to form a first core unit,

(E) at least a second plurality of said pair-s being cabled together ina helix having a length of lay exceeding the length of lay of any of thecomponent pair twists .to form a second core unit,

(F) said core units being helica'lly twisted together to form a cablecore, and

(G) a sheath surrounding said core.

4. A communication cable comprising a large number of twisted pairs ofinsulated conductors,

(A) all of said pairs of conductors being twisted with the samedirection of lay,

(B) each conductor being individual-1y wrapped with an approximatelydouble layer of spiralled insulating paper having a length of wrappinglay equal to the length of lay of twist of the pair comprising saidconductor,

(C) a first plurality of said pairs being cabled together in a helixhaving a length of lay exceeding the length of lay of any of thecomponent pair twists to form a first core unit,

(D) the direction of spiral of the paper on all conductors in said cablebeing the same,

(E) at least a second plurality of said pairs being cabled together in ahelix having a length of lay exceeding the length of lay of any of thecomponent pair twists to form a second core unit,

(F) said core units being helically twisted together to form a cablecore, and

(G) a sheath surrounding said core.

No references cited.

LEWIS H. MYERS, Primary Examiner.

1. A COMMUNICATION CABLE COMPRISING A LARGE PLURALITY OF TWISTED PAIRSOF INSULATED CONDUCTORS, (A) ALL OF SAID PAIRS OF CONDUCTORS BEINGTWISTED WITH THE SAME DIRECTION OF LAY, (B) EACH CONDUCTOR BEINGINDIVIDUALLY WRAPPED WITH AN APPROXIMATELY DOUBLE LAYER OF SPIRALLEDINSULATING TAPE HAVING A LENGTH OF WRAPPING LAY EQUAL TO THE LENGTH OFLAY OF TWIST OF THE PAIR COMPRISING SAID CONDUCTOR, (C) THE DIRECTION OFSPIRAL OF THE TAPE ON ALL CONDUCTORS IN SAID CABLE BEING THE SAME, (D)SAID PAIRS BEING CABLE TOGETHER IN A HELIX HAVING A LENGTH OF LAYEXCEEDING THE LENGTH OF LAY OF ANY OF THE COMPONENT PAIR TWISTS, AND (E)A SHEATH SURROUNDING SAID CABLED CONDUCTORS.